1. Field of The Invention
The present invention relates generally to a treatment method for treating an object to be treated and a treatment equipment therefor.
2. Description of The Prior Art
Important processes for manufacturing objects to be treated, e.g., semiconductor wafers, include heat treatment processes. Such heat treatment processes include, e.g., formation of oxide films on semiconductor wafers, diffusion of dopant, annealing and CVD. In recent years, vertical treatment equipment (vertical treating furnace) has been often used in the heat treatment processes in place of horizontal treating furnaces, since vertical treatment equipment has the advantage of small entrainment of air and so forth.
As shown in FIG. 8, such a vertical treatment equipment comprises: a vertical heat treating furnace 11; a wafer boat 12 serving as a wafer holder for holding a plurality of wafers W arranged so as to be vertically apart from each other at regular intervals; a delivery rack 13 for mounting thereon a wafer carrier (which will be hereinafter simply referred to as a "carrier") C to deliver the wafers W; a carrier inlet/outlet port (not shown); a carrier stocker (not shown) and so forth. The wafers W in the carrier C mounted on the delivery rack 13 are transferred to the wafer boat 12 by means of an arm 14 of a transfer robot. After a predetermined number of wafers are loaded on the wafer boat 12, the wafer boat 12 is moved upwards to be carried in the heat treating furnace 11 by means of a boat elevator (not shown), so that a predetermined heat treatment of the wafers W is carried out in the heat treating furnace 11.
The upper and lower end portions of the wafer boat 12 have a lower temperature than those of other portions of the wafer boat 12 due to the structure of the heat treating furnace 11. Therefore, in order to avoid the ununiformity of treatment between the wafers W, dummy wafers are usually arranged at the upper and lower end portions of the wafer boat 12, and wafers to be treated are usually loaded at the other portions of the wafer boat 12.
For example, in a case where wafers W arranged at a certain lot are heat-treated, in order to prevent the subsequent processes of the wafers W at that lot from being wasted, it is required to preliminarily determine if a predetermined heat treatment was carried out. Therefore, in conventional wafer monitoring methods, a monitor wafer W is loaded in a wafer loading region of the wafer boat 12, in which the wafers to be treated are loaded. After heat treatment, the monitor wafer is inspected to indirectly grasp the treated state of wafers to be treated, which have been heat-treated with the monitor wafer.
FIG. 9 shows an example of a conventional monitoring method for monitoring wafers to be treated. In this method, for example, a monitor wafer M1 (M2, M3), together with wafers W to be treated, is housed in a carrier C. After heat treatment, the respective wafers W are returned to the original carrier, and the treated state of the monitor wafer M1 (M2, M3) is inspected to indirectly grasp, e.g., the treated state of the wafers W to be treated, which are contained in the carrier C housing therein the monitor wafer M1 (M2, M3), so that it is determined whether the wafers W to be treated should proceed to the next process.
The heat treatment conditions in the heat treatment equipment are not always stable, and may be suddenly or gradually deteriorated. Therefore, in order to prevent wasteful processes from being subsequently carried out or in order to prevent the operation of the heat treatment equipment from being stopped in a usual operating time zone, it is important to always monitor the state of the heat treatment equipment. However, according to the conventional heat treatment methods, it is very inconvenient to always monitor the heat treatment equipment for the following reasons. Since the reference level of the process for inspecting the state of heat treatment, e.g., the in-plane uniformity of the thicknesses of the wafers and the number of particles thereof, on the basis of the monitor wafer is different from that of the process for inspecting the state of the heat treatment equipment, it is difficult to carry out these inspection processes by a single stage of inspection. For that reason, two stages of inspection processes must be always carried out to inspect the state of the heat treatment equipment using the monitor wafer. Thus, the inspection for both heat treatment and equipment testing is performed on the same monitor wafer known in the art. The inspection of the wafer occurs after removal of the heat treatment equipment so that the wafers must be moved from the processing during the inspection. Therefore, during the inspection processes, the wafers to be treated, which are arranged in the lot containing the monitor wafer, can not proceed to the next process, so that the through put of the whole process is lowered.
In addition, if a sequence monitor for inspecting the state of the equipment on the base of the monitor wafer in a certain cycle, i.e., every few processes, is carried out, the operator must count the number of processes and supply a monitor wafer to the inspection process of the state of the equipment every time the predetermined number of processes is carried out, so that the operator's work is complicated. Moreover, if it is determined in accordance with the number of processes whether the monitor wafer proceeds to the next process after inspecting the treated state or after inspecting the state of the equipment, it is very difficult to apply this to the a mass production process. For that reason, the state of the equipment has not been adequately monitored.
Thus, in the conventional heat treatment methods,there is lacking the required monitoring for keeping abreast with the state of the equipment. Accordingly, periodic maintenance is carried out or maintenance is carried out after the operation of the equipment is stopped when abnormal data continuously appears.